82 



NA TURE 



[November 24, 1904 



I 



meteorites, however, more extended treatment is required. 

 I have taken the resistance to be in direct proportion to 

 the density of the air. To do even this requires a l<now- 

 ledge of the density at all altitudes, and for this I have 

 assumed an isothermal distribution of temperature. The 

 theory of adiabatic distribution makes the atmosphere cease 

 at distances well within twilight and meteor phenomena, 

 and is therefore of no use. Probably something between 

 these two would be most accurate, but its precise form is 

 not of great importance in this investigation owing to the 

 very slight influence of the uppermost reaches of the air 

 on the motion of meteorites. 



I now come to the meteorites themselves. Many sizes 

 have been considered, but chiefly diameters of o lo inch 

 and 12 o inches. I refer to these as the " small " and the 

 " large " meteorites. When other sizes are mentioned 

 their diameters are given. I have further taken two 

 materials, viz. iron and stone (trap rock), representing 

 holosiderites and asiderites. The thermal constants for 

 the materials are those found by Forbes. 



I stated above the circumstances in which a knowledge 

 of the heat energy given to the meteorite might be taken 

 to be known. To find the temperature distribution in the 

 interior of the iron or stone I have adopted the approxi- 

 mation of considering the meteorite to be cylindrical, and 

 then utilising ordinary cylindrical coordinates. During the 

 investigation a good many results were obtained which in- 

 dicated methods by which the simple labour of the work 

 could be lightened. Some of the more cumbersome ex- 

 pressions could be simplified by dividing the distance between 

 the earth's surface and infinity into two regions, that within 

 the sensible effect of the atmosphere and that without. 



Many results were obtained during the investi- 

 gation. In the large meteorite it was found that for 

 all velocities of approach the temperature at the centre 

 was a most minute fraction of that at the surface. For 

 the small meteorite it was found that the final velocity was 

 always very small and the time of flight correspondingly 

 great, with the result that the whole of the material would 

 be consumed before reaching the earth's surface — this would 

 then properly be termed a meteor, not a meteorite. In its 

 turn this consideration gives the altitude at which incan- 

 descence would occur. The small iron meteor would burst 

 into brilliance at 45 miles up, and the stone one at 68 miles. 

 To obtain a superior limit to the point of incandescence I 

 assumed a meteor the diameter of which was only a 

 millionth of an inch. For iron, brilliancy is obtained at I 

 106 miles, and for stone at 129 miles. These figures are 

 obtained by assuming the meteors to have the maximum 

 velocity which the earth could impose. If, however, an 

 initial velocity of 250 miles per second be assumed, surely 

 a superior limit, incandescence would occur some 35 or 40 

 miles further off, so that the greatest height for visibility 

 w-ould lie well within some 170 miles. 



An iron meteorite 3 inches in diameter falling to the 

 earth from an infinite distance would begin to get warm 

 about nine seconds before reaching the earth, and continue 

 to increase in temperature for about seven seconds, after 

 which its velocity would be practically " killed," and two 

 seconds later it would reach the earth at about two-thirds 

 of a mile per second. This represents a typical case for 

 what might be termed the " twelve pound shell " size. 



In the " twelve pound shell " size the internal temperature 

 falls off very rapidly towards the interior. Thus, taking 

 the mean temperature in the severest case as i-oo, the 

 surface temperature was 22, and at a depth equal to a 

 fifth of the radius (030 inch) the temperature was about 

 03 only, whilst at the centre it was 00016. So that for 

 the most excessive surface temperatures the central tempera- 

 ture would be well below the temperature of liquid air, 

 assuming, of course, that the initial temperature of the 

 meteorite is at the absolute zero. 



The steepness of the heat gradient at or near the surface 

 is the probable cause of the nodular appearance of 

 meteorites. Great resistance to the inward flow of heat 

 would be offered by any internal veining, and as a result 

 such surfaces of separation would tend to become the limit- 

 ing surfaces for any burning which might occur. 



The various formula; used to obtain the above results 

 were suited to a subsidiary investigation, viz. that of the 

 problems connected with the ejection of rock from terrestrial' 



NO. 1830, VOL. 71] 



volcanoes. . The results of such an investigation may be 

 briefly summarised as follows : — Had the earth no atmo- 

 sphere all masses shot off vertically at 7 miles a second 

 and over would fail to return. With the existing atmo- 

 sphere the large meteorite would require a velocity of 13 

 miles per second, and the " twelve pound shell " would 

 want a velocity of 78 miles per second. These velocities 

 are not without interest in view of the theory that 

 meteorites originated from terrestrial volcanoes. Smaller 

 velocities would suffice were the masses discharged 

 from high altitudes. Thus, from a height of 5 miles, 

 the velocity for the large iron meteorite would be only 

 83 miles per second, and for the " twelve pound shell " 

 only 18 miles a second. F'urther calculation shows that 

 with an initial velocity of 7 miles a second the large 

 meteorite would rise to only some 120 miles, and the 

 " twelve pound shell " to between 40 and 50 miles, and both 

 would then fall back to the earth. 



^In conclusion, the result oT the investigation may be said 

 to have created a strong presumption in favour of the 

 following general deductions : — 



(a) That the velocities of meteorites are materially changed 

 by the resistance of the atmosphere, and, in general, by a 

 fractional part of the velocity which is independent of the 

 velocity of approach. 



(b) That the superior limit for incandescence is probably 

 about 150 miles above the earth's surface. 



(c) That no iron meteor the original weight of which was 

 less than 10 to 20 lb. reaches the earth's surface, and that 

 when a meteor does do so the temperature of its centre is 

 not in general above that of liquid air (assuming the 

 ^emperature of space to be zero). 



I am aware that the whole structure of the investigation 

 rests on the evil principle of extrapolation, but until man 

 is capable of experimenting with velocities of 10 or 20 miles 

 a second, and surviving thereafter to record his results, no 

 other manner of investigation seems possible. 



London, November 13. H. E. Wimperis. 



Mount Everest : the Story of a Controversy. 



I HAVE read with interest in your columns under this 

 title a carefully compiled and instructive account of the 

 discussions that have from time to time during the past 

 fifty years broken out with regard to the naming of the 

 highest measured point on the earth's surface, Peak XV of 

 the Indian Survey. 



1 have long maintained it to be a matter for regret that the 

 monarch of mountains should be called after any individual, 

 however eminent, and I am still of this opinion, which 

 is shared by most mountaineers and mountain lovers. We 

 should prefer that Peak XV should bear a Nepalese or a 

 Tibetan name, even had one to be invented for it, as twenty 

 years ago Alpine Clubmen, in accord with Russian surveyors, 

 found or invented native names for many of the great peaks 

 of the Caucasus. 



But, since your correspondent appeals to me not to prolong 

 the controversy further, I must remind him that the opinion 

 I have expressed is an individual and not an official opinion. 

 For ten years I have had no official connection with the 

 Royal Geographical Society. 



Should the council of that body resolve that, considering 

 the length of time the title " Mount Everest " has been more 

 or less in use in this country for Peak XV, the absence of 

 any evidence that that individual peak is designated as, or 

 included in the designation of, Gaurisankar by the Nepalese, 

 and the practical inconvenience (whether the name be 

 authentic or not) of introducing a new Tibetan name such 

 as Chomo- or Jamokangkar, it is expedient that the title 

 Mount Everest should be generally accepted, I shall 

 acquiesce. For I attach greater importance to the general 

 principle than to the particular case, and I believe the pro- 

 tracted discussion and many protests summarised in your 

 columns have served their purpose in helping to discourage 

 the practice of giving personal names to mountains. 



I should add that foreign geographers are not, as your 

 correspondent suggests, mainly dependent on the Geo- 

 graphical Journal for information in this matter. Captain 

 Wood's report has been noticed in that well known periodical 

 Pctermann's Mitleilungcn. 

 , , ^ DOLGLAS W. Freshfield. 



